Okay I am having an issue with my car. It will turn on and at times run fine, but almost all the time, when I idle, the engine will almost stall and bounce back and just keep going over and over again. It drops to just under 500rpm and then bounces back to 1000 and just keeps doing it repeately. Anyone have any idea what could be causing this? I will be replacing the sparkplugs today but i don't think that this is really an issue.

coupe

06-05-2007, 01:23 PM

ALOT of people have this problem (myself included) and no one has ever found a fix.

onesexyga

06-05-2007, 02:47 PM

Same thing happens to me. Especially when i start it warm, like after i get gas. Dips to 500 rpm, then bounces back up. I heard from someone it could be a maf sensor. Do you have a CAI?

Panacea

06-05-2007, 03:02 PM

Don't know if it's the same problem I was having, but tap the gas and see if it settles the idle back to normal.

Sprucegagt

06-05-2007, 03:20 PM

Vacuum leak/TPS/MAF any or all could be the culprit.

coupe

06-05-2007, 04:10 PM

Vacuum leak/TPS/MAF any or all could be the culprit.

Yeah until you change all that with new parts and it still does it.
Ive replaced everything there is to replace and it never fixes it. It started doing it at 45K miles and has ever since.

If you run a search you will see alot of people have this problem and no one has found a fix.

What sucks even more.....it never throws a code.

EBlend

06-05-2007, 04:14 PM

Same thing happens to me. Especially when i start it warm, like after i get gas. Dips to 500 rpm, then bounces back up. I heard from someone it could be a maf sensor. Do you have a CAI?

i don't have a cai anymore but did at one point. I heard from a buddy who used to work in a gm dealership that the oil used to grease up the k&n filters is very bad for 3400 sensors, but it seems the whole problem started happening after I took out my car out of parking last year and run some seafoam through it. Some people say that seafoam ruins your plugs so I will try to see if new plugs will do anything, but i am doubtful

coupe

06-05-2007, 04:44 PM

Mine started doing it LOOOOOOONG before i modded it.

Sprucegagt

06-06-2007, 06:41 AM

Yeah until you change all that with new parts and it still does it.
Ive replaced everything there is to replace and it never fixes it. It started doing it at 45K miles and has ever since.

If you run a search you will see alot of people have this problem and no one has found a fix.

What sucks even more.....it never throws a code.

Ever hook up a scanner, like Autotap, to monitor TPS voltage / Long Term Fuel Trim at idle? I'd like to help out more, but I've never had this problem unless I've caused it.

EBlend

06-19-2007, 05:46 AM

So I replaced the plugs and thought the problem went away, until yesturday and it started doing it again. This is so frustrating. I am never buying a GM vehicle again unless its a high end one. I guess it is time to start replaceing everything peice by peice until I find what it causing the issue.

Sprucegagt

06-19-2007, 06:26 AM

Yeah until you change all that with new parts and it still does it.
Ive replaced everything there is to replace and it never fixes it. It started doing it at 45K miles and has ever since.

If you run a search you will see alot of people have this problem and no one has found a fix.

What sucks even more.....it never throws a code.

Just a side note. But I have had brand new TPS sensors fail straight out of the box.

EBlend

06-19-2007, 08:20 PM

I tested a few things today and still having the problem. Tested the TSP and that looked very good, just like the repair manual said, with proper voltages displayed and no variation and all that. There is a device that you can plug into your car and go for a drive and it records all of your sensor information, would this be beneficial for me to do and would that information help me pinpoint the problem?

Also, could a clogged cat converter possibly cause this?

Lab Rat

06-20-2007, 05:23 AM

I replaced my cat about 2 months ago, still tries to die occasionally.

AmbrosiaCaress

06-22-2007, 01:36 PM

My own 99 GAGT does this... Only when it is warm... like after getting gas (as a previous poster stated)... Sometimes the car actually does die, and starts hard, other times it just bounces low to normal, low to normal...

I had the TPS sensor replaced, no real change...

Gotta love GA's and their quirks...

andrewe77

06-23-2007, 11:18 PM

Mine does it occasionally. My humble engineering opinion is that the computer sometimes gets into a feedback loop with the IAC valve where it is overshooting the target RPM. It will continue to do this until the input to the loop is changed such as tapping the throttle or putting it into gear.

videoman

06-23-2007, 11:28 PM

Freind had a similar issue. I took off the MAF cleaned it ( very carefully ) with some Qtips and reset the PCM. So far its been over 5000KMS and he hasn't had the issue return.

WeibSunder

06-24-2007, 12:00 AM

The only time I've had this problem is when I tried putting gas in my GA while it was running. Other than that I haven't had this problem thank God.

onesexyga

09-15-2007, 12:37 PM

Sorry to dig it up, but any updates on this? mine is getting worse. Doesnt just do it on restarts, just does it at idle.

ss88

09-15-2007, 04:05 PM

I have the same problem too... After a restart, like a short trip (or getting gas as you guys are saying) But I havn't found a solution. However, When I was running my engine and was in that kind of mood I was looking around and I thought I'd check my oil too. When I took the cap off the crankcase to add oil the rpm's dropped. Some sort of pressure difference within the engine must of caused this.

nickofcourse

09-15-2007, 06:16 PM

when my fathers van was running really bad it was moisture that got into the spark plug module?

idk do our cars have a spark plug module?

Panacea

09-15-2007, 10:06 PM

Mine does it occasionally. My humble engineering opinion is that the computer sometimes gets into a feedback loop with the IAC valve where it is overshooting the target RPM. It will continue to do this until the input to the loop is changed such as tapping the throttle or putting it into gear.

That sounds like a logical explaination to me...

Freind had a similar issue. I took off the MAF cleaned it ( very carefully ) with some Qtips and reset the PCM. So far its been over 5000KMS and he hasn't had the issue return.